Pfeile in die Galerie einbinden

<?php
/**
 * Template Name: Gemälde
 *
**/
?>


<?php
    $categories = get_terms( 'years', array('hide_empty' => 0, 'order' => 'DESC') );
    error_reporting(E_ALL);
    ini_set('display_errors', 'on');
    wp_redirect( get_term_link($categories[0]), 301 );
    exit;
?>


<?php get_header(); ?>
    <?php if (have_posts()) : ?>
        <?php while (have_posts()) : the_post(); ?>
        
        <div class="main-page">
            <div class="container-fluid">
                <div class="page-body">
                    <div class="top-filters">
                        <ul class="filter clearfix">
                            <?php /*?><li class="active"><a href="#" data-filter="*"><?php echo __('Alle', 'meyer'); ?></a></li><?php */?>
                            <?php
                                $categories = get_terms( 'years', array('hide_empty' => 0, 'order' => 'DESC') );
                                foreach ($categories as $category) {
                                    //echo '<li><a href="#" data-filter=".y'.$category->slug.'">'.$category->name.'</a></li>';
                                    echo '<li><a href="'.get_term_link($category).'">'.$category->name.'</a></li>';
                                }
                            ?>
                        </ul>
                    </div>
                    <div class="row isotope-list-row">
                        <div class="portfolio-mansonry-container gallery" data-layout="masonry">
                            <?php
                                $loop = new WP_Query( array( 'post_type' => 'painting', 'posts_per_page' => -1 ) );
                                while ( $loop->have_posts() ) : $loop->the_post();
                                    $id_post = $loop->post->ID;
                                    $src = wp_get_attachment_image_src( get_post_thumbnail_id($id_post), 'full' );
                                    $thumbnail_image = get_posts(array('p' => get_post_thumbnail_id($id_post), 'post_type' => 'attachment'));
                                    //var_dump($thumbnail_image);
                                    ?>
                                    <a href="<?php echo $src[0]; ?>" rel="<?php echo synth_list_product_categories($id_post); ?>" data-caption="<?php echo $thumbnail_image[0]->post_title; ?><br /><?php echo $thumbnail_image[0]->post_excerpt; ?><br /><?php echo $thumbnail_image[0]->post_content; ?>" class="fancy-image portfolio-masonry-item col-md-3 col-sm-4 col-xs-6 <?php echo synth_list_product_categories($id_post); ?>">
                                        <?php the_post_thumbnail( 'large'); ?>
                                    </a>
                                    <?php
                                endwhile;
                                wp_reset_query();
                            ?>
                        </div>
                    </div>
                    <?php //the_content(); ?>
                </div>
            </div> <!-- /.container -->
        </div>
        
        <?php endwhile; ?>
    <?php endif; ?>
<?php get_footer(); ?>